Heated/Cooled Seats Inoperative-(Split For Indexing)-Part 1
Heated/Cooled Seats Inoperative
Diagnostic Instructions
* Perform theDiagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The heat and cool seat functions for the driver and passenger seats are controlled by the climate control seat module (CCSM) that is located under the passenger seat cushion. When a driver or passenger heat or cool seat switch is pressed, a low reference signal is applied through the switch signal circuit to the door lock/window switch. In response to the switch input, the door lock/window switch simultaneously illuminates the appropriate heated/cooled switch indicators and sends a serial data message to the memory seat module (MSM) indicating the heat or cool seat request. The MSM then sends a pulse width modulation (PWM) signal through the appropriate heated/cooled seat mode signal circuit to the CCSM. The CCSM then applies battery positive voltage to the seat cushion and seat back thermal electronic devices (TEDs) and a pre-determined voltage to the blower motors. To determine seat temperature, the CCSM supplies a 5 V signal and a low reference to the temperature sensors that are attached to each TED. The temperature sensors are variable resistors, their resistance changes as the temperature of the seat changes. Then based on the seat temperature, the CCSM controls the voltage level that it applies to the TEDs and blower motors.
Diagnostic Aids
The following conditions must be met in order to perform valid tests when diagnosing the climate control seat system:
* The ignition must be cycled OFF then ON between each test in order to reset the CCSM.
* Most circuit faults will set a DTC within 1.5 minutes. However, some circuit faults may cause a performance problem in one mode and be inoperative and set a DTC in another mode. In some cases it may take 5 minutes or more for a DTC to set. Operate the heated/cooled seat in each of the three modes for 5 minutes or more then check for DTCs.
* The engine must be running in order to supply the CCSM with the amount of current needed to operate the heated/cool seat system.
Reference Information
Schematic Reference
Heated/Cooled Seat Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Heated/Cooled Seats Description and Operation (Heated/Cooled Seats Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. If both, the driver and passenger heated and cooled seats are inoperative, refer to Driver and Passenger Heated/Cool Seats Inoperative.
2. Ignition ON, observe the scan tool Driver Door Switch parameters listed below while pressing and releasing the appropriate switch. The readings should change between Inactive and Active or Off and ON.
* Seat Back Heat Mode Sw.
* Seat Cool Mode Switch
* Seat Heat Mode Sw.
• If the reading does not change between Inactive and Active or Off and ON, refer to the Heated and Cooled Seat Switch component test. If the switch tests normal, replace the driver door lock/window switch.
3. Observe the scan tool Passenger Door Switch parameters listed below while pressing and releasing the appropriate switch. The readings should change between Inactive and Active or Off and ON.
* Seat Back Heat Mode Sw.
* Seat Cool Mode Switch
* Seat Heat Mode Sw.
• If the reading does not change between Inactive and Active or Off and ON, refer to the Heated and Cooled Seat Switch component test. If the switch tests normal, replace the front passenger door lock/window switch.
4. If all heated and cooled seat functions operate normal, but the heated/cooled seat switch indicators do not illuminate or are always ON, refer to the Heated and Cooled Seat Switch component test. If the switch tests normal, replace the appropriate door lock/window switch.
Circuit/System Testing
Driver and Passenger Heated/Cool Seats Inoperative
1. Ignition OFF, disconnect the X1 harness connector at the CCSM.
2. Verify that a test lamp illuminates between the ground circuit terminal M and B+.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Verify that a test lamp illuminates between the B+ circuit terminal E and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
4. Disconnect the X2 harness connector at the CCSM.
5. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 1 and ground.
• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
6. If all circuits test normal, replace the CCSM.
Driver Heated/Cool Seat Inoperative
1. Ignition OFF, disconnect the X1, X2, X3 harness connectors at the CCSM.
2. Connect a test lamp between the signal circuit terminal 14 X3 and B+.
3. Ignition ON, press the HEAT or COOL seat switch through the high, medium, and low positions to OFF. The test lamp should illuminate until the OFF position is reached.
• If the test lamp does not illuminate, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the MSM.
• If the test lamp remains ON with the switch in the OFF position, test the signal circuit for a short to ground. If the circuit tests normal, replace the MSM.
Note
If the resistance is measured with the seat still warm or cool, the resistance values will vary. At 68°F, (20°C) the nominal resistance value is 1200 Ω ±5 percent . For warmer or cooler ambient temperatures, refer to the Temperature vs Resistance table below. The delta resistance values between the seat cushion and seat back temperature sensors should not be greater than 2000 Ω.
4. Ignition OFF, test for 300 Ω - 18 kΩ between the signal and low reference circuits listed below:
* Seat cushion temperature sensor signal circuit terminal 7 X2 and low reference circuit terminal 8 X2.
* Seat back temperature sensor signal circuit terminal 9 X2 and low reference circuit terminal 10 X2.
• If less than the specified range, test for a short between the signal and low reference circuits. If the circuits test normal, test or replace the appropriate seat cushion or seat back heat/cool seat ventilation blower.
• If greater than the specified range, test the signal and low reference circuits for a short to voltage or an open/high resistance. If the circuits test normal, test or replace the appropriate seat cushion or seat back heat/cool seat ventilation blower.
Note
The test leads must be connected in the correct polarity, otherwise lower out of range values will appear. Use the Positive Lead for the COOL control circuit and the Negative Lead for the HEAT control circuit. If the resistance is measured with the seat still warm or cool, the resistance values will vary even if the system was powered up for just a few seconds. The TED must be allowed to stabilize to room temperature prior to a measurement. The conditions listed below will change the resistance to out of range values:
* The test leads are incorrectly connected.
* Air blowing across the TED.
* Measuring the resistance at other than room temperature of 70°F (21°C).
* Holding the TED portion of the heat/cool seat ventilation blower in your hand.